This invention is directed to a neurostimulator that is preferably implantable and is suitable for treating epilepsy and other neurological disorders. The invention includes inventive leads that are suitable both for providing electrical somatosensory stimulation, extradurally applied, as well as electrical stimulation that is applied to the central nervous system. The leads are preferably also suitable for sensing electrical signals in the brain. The invention includes processes of using the neurostimulator and its leads.
The neurostimulator may independently provide a variety of different electrical stimulation, e.g., non-responsive electrical stimulation signals applied to the central nervous system to reduce the likelihood of a seizure or other undesirable neurological even from occurring, electrical stimulation signals applied to the central nervous system when the neurostimulator determines that epileptiform waveforms are impending or extant, and extradural electrical somatosensory stimulation signals.
The responsive electrical stimulation signal or signals are intended to terminate epileptiform activity, e.g., to desynchronize abnormally synchronous brain electrical activity.
Epileptic seizures are characterized by hypersynchronous neuronal activity. Neurologists recognize a wide variety of seizures. Partial onset seizures begin in one part of the brain; general onset seizures arise throughout the entire brain simultaneously. When partial onset seizures progress to involve much of the brain, they are said to have xe2x80x9csecondarily generalized.xe2x80x9d Some seizures result in the loss of conscious awareness and are termed xe2x80x9ccomplexxe2x80x9d seizures. So-called xe2x80x9csimplexe2x80x9d seizures may involve other symptoms, but consciousness is unimpaired. Seizure symptoms may include sensory distortions, involuntary movements, or loss of muscle tone. The behavioral features of seizures often reflect a function of the cortex where the abnormal electrical activity is found.
Physicians have been able to treat epilepsy by resecting certain brain areas by surgery and by medication. Brain surgery is irreversible, and is either ineffective or is associated with neural morbidity in a sizable percentage of cases. Medication is the most prevalent treatment for epilepsy. It is effective in over half of patients, but in the reminder of the patients, the medication is either ineffective in controlling seizures, or the patients suffer from debilitating side effects. A promising method of treating patients having epileptic seizures is electrical stimulation of the brain.
Since the early 1970""s, electrical brain stimulators have been used which provide more or less constant stimulation, the stimulation largely being unrelated to detected electrical activity.
Electrical stimulation of the nervous system has been used to suppress seizures. A device is described in Cooper et al. for stimulation of the cerebellum. See, xe2x80x9cThe Effect of Chronic Stimulation of Cerebellar Cortex on Epilepsy and Man,xe2x80x9d I. S. Cooper et al in The Cerebellum, Epilepsy and Behavior, Cooper, Riklan and Snyder Edition, Pleman Press, N.Y. 1974. Others have utilized devices which stimulated the centro median nucleus of the thalamus. See, xe2x80x9cElectrical Stimulation of the Centro Median Thalamic Nucleus in Control of Seizures: Long Term Studies.xe2x80x9d F. Valasco et al, Epilepsia, 36 (1): 63-71, 1995. Chaos Theory has been used to apply stimulation to a seizure focus in vitro to abort the seizure. See, S. Schiff et al, xe2x80x9cControlling Chaos in the Brain,xe2x80x9d Nature, Volume 370, Aug. 25, 1994.
Non-responsive electrical stimulation devices have been used for significant periods. The devices and procedures did not constitute a panacea, however. For instance, a 17 year follow-up study shown in Davis et al. (xe2x80x9cCerebellar Stimulation for Seizure Control 17 Year Study,xe2x80x9d Proceedings of the Meeting of the American Society for Stereotactic and Functional Neurosurgery, Pittsburgh, Pa., Jun. 16-19, 1991 and in Stereotact. Funct. Neurosurg. 1992; 58; 200-208) showed that less than one-half of the patients became seizure free, even though 85% showed some benefit.
Responsive brain stimulation, specifically electrical stimulation that is applied to the brain, has not yet been used to treat patients in long-term studies. This is true even though there are algorithms suitable for detection of the onset of an epileptic seizure. For instance, Qu et al provide an algorithm said to recognize patterns of electrical activity similar to those developed while recording an actual epileptic seizure. See, Qu et al., xe2x80x9cA Seizure Warning System for Long-Term Epilepsy Monitoring, Neurology,xe2x80x9d 1995; 45:2250-2254. Similarly, Osorio, et al. have suggested an algorithm applied to signals from intracranial electrodes with good results. See Osorio, et al. xe2x80x9cA Method For Accurate Automated Real-Time Seizure Detection,xe2x80x9d Epilepsia, Vol. 35, supplement 4, 1995.
Finally, in conjunction with direct brain tissue stimulation, electrical signals that are applied to regions of the body which are not neurological tissue, e.g., applied extradurally to the skin and particularly to the scalp, have been shown to be useful in delaying or preventing the onset of a seizure.
In applying the various electrical stimuli to the brain, a number of different electrode configurations are known.
U.S. Pat. Nos. 4,702,254, 4,867,164, and 5,025,807, each to Zabara, show a device for controlling or preventing involuntary movements such as caused by epileptic seizures. The device is made up of an electrical pulse generator, a positive electrode to be applied to a person""s body, and a negative electrode to be placed adjacent the vagus nerve in that body.
U.S. Pat. No. 4,735,208, to Wyler et al., shows a subdural strip electrode for determining epileptogenic foci. The strip has a long, tapered proximal end portion terminating in a narrow tip from which a number of wires extend. This is said to allow withdrawal of the strip electrode without a substantial incision. Strip width and thickness are said to be such that the strip may be withdrawn after extended implantation without the need for surgery. In one variation, the central region of the strip is significantly reinforced.
U.S. Pat. No. 4,903,702, to Putz, shows an electrical brain-electrode device for increased accuracy in determining epileptogenic foci. This device has a dielectric base member and an array of electrodes mounted on that base member. Each of the electrodes has a separate wire for connection to a measurement device. The device preferably has radio-opaque regions adjacent to at least one of the electrodes such that the position of the electrodes with respect to the brain may be more readily determined by x-ray.
U.S. Pat. No. 5,097,835, also to Putz, shows a subdural electrode for determining epileptogenic foci. The device is said to have dielectric layers and at least one electrode disc placed between the layers. The disc includes a tab. The accompanying lead wire is folded over the outer segment of the tab so that the tab crimps the wire. The electrical and mechanical integrity of the connection is improved by wrapping the wire about the tab several times before crimping.
U.S. Pat. Nos. 5,702,429, 5,814,092, and 5,913,882, each to King, show a neural stimulation technique with feedback and further shows a variety of stimulating and recording leads (e.g., #10 in FIG. 1 discussed at column 2 beginning at line 21) and other embodiments shown in FIGS. 2-5. King shows (beginning at column 3, line 60) the manner of using the stimulating electrodes (18-21) and the recording electrodes (25-26). Generally, the placement of the electrodes is said to be xe2x80x9cat sites adjacent electrically excitable tissue for control of conscious paresthesia into the painful area of a patient.xe2x80x9d The patent goes on to explain that: xe2x80x9celectrically excitable tissue includes neural tissue intrinsic to the heart and other organs, a peripheral nerve, the spinal cord surface, the interior of the spinal cord, deep brain tissue, brain surface tissue, and neural ganglia.xe2x80x9d See, column 3, line 5 following.
U.S. Pat. No. 5,782,798, to Rise, shows a device for dispersing one or more drugs and/or electrical stimulation to treat eating disorders. The treatment is carried out with an implantable pump and a catheter having a proximal end coupled to the pump. The catheter may have stimulation electrodes (38 and 40 in FIG. 3). The stimulation electrodes may in some instances serve as reference electrodes as well.
U.S. Pat. No. 5,800,474, to Benabid et al., shows a method and apparatus for providing high frequency electrical stimulation pulses to the subthalamic nucleus to block neural activity in the subthalamic nucleus and reduce excitatory input to the substantia nigra which is said to lead to an overall reduction in occurrence of seizures. The device used there is a lead (22A in the Figure) having four stimulation electrodes (115) implanted into a portion of the basal ganglia of the brain.
U.S. Pat. No. 5,843,093, to Howard III, shows a dual purpose multi-electrode neuron-monitoring electrode assembly which may also be used to deliver drugs to the brain. The device is used particularly for selectively inactivating specific regions of the brain using ablative surgery. In addition, the device is used as a neural prosthetic device for the auditory cortex apparently to resolve deafness problems. The various devices of interest are generally shown in FIGS. 6 through 11B.
U.S. Pat. No. 5,843,148, to Gijsbers et al., shows a high resolution brain stimulation lead which is able to stimulate exclusively certain selected small neurological targets without damage to the involved brain tissue. The structure is best shown in FIGS. 2, 3A and 3B.
U.S. Pat. No. 5,902,236, to Iversen, shows a tissue electrode for both monitoring tissue electrical activity and for stimulating that tissue. The electrode is designed to be inserted subdurally. The electrode itself is generally either a rhombus or a half rhombus in shape.
U.S. Pat. No. 5,938,689, to Fischell et al., shows a configuration of electrodes for stimulation of brain tissue. Generally the device includes a configuration of electrodes having at least one electrode on the brain surface and at least one additional electrode located deep within the tissue of the brain. Each electrode includes its own lead, as is typically the practice.
U.S. Pat. No. 6,006,124, to Fischell et al., shows a variety of ways of placing electrodes subdurally.
U.S. Pat. No. 6,024,702, shows an implantable electrode assembly made using a flexible printed circuit base. The non-conducting backing material is preferably a material such as Mylar or Silicone.
U.S. Pat. No. 6,094,598, to Elsberry et al., shows a method and a device for treatment of specific neural disorders resulting in abnormal motor response, by means of an implantable signal generator and electrode in an implantable pump and catheter. The various forms of the electrodes which are implantable in the brain. Various configurations for the implantable electrodes are shown in FIGS. 12-17.
None of the cited documents describes the devices and procedures claimed herein.
This invention deals with a combination lead having multiple electrodes configured both to provide extradural somatosensory electrical stimulation to an electrically sensitive region of a human body and to provide intracranial electrical stimulation to the brain. The combination lead is made up of an elongate member having a distal end that preferably is round or flattened in cross-section. The lead also has a proximal end. At least one distal electrode is located relatively distally of the proximal somatosensory electrode on said elongate member for providing electrical stimulation to said human brain. At least one somatosensory stimulation electrode is located relatively more proximal with respect to the distal electrode(s) on said elongate member and is further situated on said elongate member to provide electrical stimulation extradurally to said electrically sensitive region of a human body when said distal electrode(s) are in contact with said human brain. A plurality of contacts (generally as a female socket or male protuberance for connecting with another junction device) is located most proximal on said elongate member. The number of contacts in junction equals in number the sum of the distal brain electrodes plus said at least one somatosensory stimulation electrode. Each of the plurality of contacts is uniquely, electrically connected to a single distal electrode or somatosensory stimulation electrode. These contacts allow connection with the implanted neurostimulator central unit.
The somatosensory stimulation electrodes preferably have an area which is substantially larger than any one of the distal electrodes. Clearly, though, such is not a requirement. The distal electrodes may be bands on a circular cross-section elongate member or flat or protruding regions located on the flat distal end. Functionally speaking, the electrodes may be any shape that provides stimulatory contact with the tissue in question. The various electrodes may be made of a biocompatible metal or alloy, preferably platinum or platinum alloys, although many other metals, e.g., gold or palladium, may be suitable.
One variation of the invention includes a neurostimulator assembly for modifying an electrical activity in a human brain. The combination may comprise the inventive combination lead, an implantable neurostimulator central unit having at least a brain electrical activity sensor for sensing electrical activity in the brain, and a electrical signal source connectable to the somatosensory stimulation electrode. The electrical signal source is capable of initiating an electrical stimulation to the somatosensory stimulation electrode which is responsive to said brain electrical activity sensed by the brain electrical activity sensor. The implantable neurostimulator central unit may also include a non-responsive electrical signal source connectable to at least one of the distal electrodes.
Finally, the invention includes methods for treating a disorder in a human brain. The procedure maybe made up of the steps of detecting at least one brain electrical activity using the neurostimulator assembly and providing at least one electrical somatosensory stimulation signal to the somatosensory stimulation electrode. Alternatively, the stimulation may be used to provide a warning of abnormal EEG""s (or potentially abnormal EEG""s) or of a problem with the implanted system, to the patient. The method may further include the steps of applying non-responsive and/or responsive electrical brain stimuli to at least one of the distal electrodes. The electrical brain activity may be detected in a variety of sites, e.g., cortically or deep within the brain.